The invention relates to a method for operating an installation of a primary industry, for example a continuous casting and rolling installation, using a computer system. Products assigned to different production orders are produced in the installation and a production plan having a plurality of method steps is generated.
The invention further relates to an installation of a primary industry, for example a continuous casting and rolling installation, using a computer system. Products assigned to different production orders are produced in the installation and the computer system is used to generate a production plan.
Such methods for operating installations of a primary industry, such as continuous casting and rolling installations, and the corresponding installations are generally known and many of them are in operation.
The known installations are subject to process-related restrictions that result, for instance, from the tool life of parts of the installation. For example, the division of the operation of the continuous casting and rolling installation into individual sequences is a consequence of such process-related restrictions.
In installations in which different production orders are processed, there are order-related restrictions. In continuous casting and rolling installations, for example, these restrictions include, e.g., a desired steel brand or a desired thickness and/or a desired width of the respective end product.
It is well known that, as a consequence of these process and order-related restrictions, it is very difficult to operate the installation optimally with different production orders in a so-called production run. For example, with regard to the utilization of an installation, the process and order-related restrictions are almost diametrically opposed, so that until now it has been almost impossible to achieve optimum operation of an installation with different orders.
In addition to manual planning, which is possible only to a very limited extent, a method and device are known from the international application WO 00/05014 A1. Here, a genetic algorithm is used to generate a sequence of different production orders in an installation. This method, however, has the drawback of long processing times and limited optimization means.
One object of the invention is to provide a method for operating an installation, for example a continuous casting and rolling installation, that enables improved or even optimized operation.
Another object of the invention is to provide a device for operating an installation, for example a continuous casting and rolling installation, that enables improved or even optimized operation.
According to one formulation of the invention, these and objects are attained by a method for operating an installation of a basic industry, using a computer system, wherein products assigned to different production orders are produced in the installation, and wherein a production plan is generated by: a) generating an initial production plan from a plurality of production orders (order selection); b) generating a sequence of the production orders stored in the production plan while taking into account process-related restrictions to which the installation and the production orders are subject (preplanning); c) generating an executable production plan that takes into account the process-related restrictions to which the installation is subject (planning); and d) optimizing the executable production plan generated (optimization).
According to another formulation, the invention is directed to a device for operating an installation of a basic industry, wherein products assigned to different production orders are produced in the installation. The device includes a computer system that: generates an initial production plan from a plurality of production orders, generates a sequence of the production orders stored in the production plan, generates an executable production plan that takes into account process-related restrictions to which the installation is subject, and optimizes the generated executable production plan.
According to the invention, the initially described problem is not solved by manual entry or by using a genetic algorithm as in the prior art, but in the form of method steps of order selection, pre-planning, planning and optimization. The particular advantage of these method steps is that they require substantially less processing time and improve the planning quality attributable to the particular method used.
In the order selection, a production plan that is composed of a plurality of production orders is generated. One advantageous embodiment of order selection is that the production orders that are included in the production plan are selected as a function of commercial and technical criteria. Such commercial and technical criteria may include, among others, delivery dates of the completed product, quality data and technical data, such as width and thickness of the end product in the case of casting and rolling installations.
The purpose of preplanning is to establish a sequence of the production orders stored in the production plan while taking into account as many restrictions as possible. In preplanning, the process-related cost incurred in switching from one production order to the next production order is calculated. A sequence of the selected production orders is defined in which the cost incurred is made as low as possible. This cost is determined as a function of the process-related restrictions to which an installation is subject.
The purpose of planning is to generate an executable production plan based on the requirements of the preplanning. In planning, the sequence defined in the preplanning remains, but other products are possibly inserted in order to meet the process-related restrictions of the installation. Planning takes into account all restrictions that exist in an installation, such as roll performance in the case of continuous casting and rolling installations.
According to another advantageous embodiment, additional products are selected from production orders that had previously been omitted in the order selection.
In a further advantageous embodiment of the inventive method, if no other products from production orders are available, the additional products are determined from production-independent orders. Production-independent orders are defined, e.g., as:
a) products of expected production orders,
b) products of recurrent, i.e., continuously occurring, production orders,
c) products that are not associated with any of the aforementioned orders.
Optimization identifies points in planning that have further optimization potential. Essentially, all of these points are points in a production plan at which additional products of independent production orders were included. To avoid these products, the original order selection is influenced in such a way that a corresponding improvement can be expected. For this new order selection, preplanning and planning are re-executed. The result after optimization is then compared with the initial result. If the optimized result at the cost determined in preplanning and planning is better, then this result is used as the new production plan. An alternative procedure in the step of optimization is to accept local deteriorations in individual installation parts in order to obtain a better overall solution.
One advantageous embodiment of the invention is that deletion of at least one production order is factored into the optimization of planning.
An advantage of this procedure (using order selection, preplanning, planning and optimization) is that all the restrictions related to the sequence of two products can be handled directly in preplanning. This makes planning highly flexible regarding possible requirements dictated by additional restrictions.
A further advantage of such an approach is that it can be used for different variants of production planning, e.g., regular planning, emergency planning, as well as residual planning.
Regular planning is defined as a production plan generated over a predefined period and taking into account both throughput restrictions and process-related restrictions, as well as quality restrictions.
In emergency planning, other restrictions in addition to the regular planning restrictions are taken into account. If technical faults occur in the installation, or if parts of the installation cannot meet the technical specifications, re-planning is carried out, possibly with restricted resources or changed boundary conditions.
In residual planning, a sequence of customer orders is specified for a production plan, i.e., the steps of order selection and preplanning are carried out manually. The other steps are performed as described in planning and optimization.
Installation restrictions that are taken into account in preplanning and planning, particularly in continuous casting and rolling installations, are set out below:
a) steel production: melt weights, scrap quantities per melt, processing times;
b) continuous casting: ingot dimensions, casting rate, frame groups, width adjustment rate, setup times, scrap quantities per casting sequence;
c) tunnel furnace: processing times;
d) hot roll mill: roll performance on heating strips, restrictions on changes in thickness, width restrictions, intermediate roll changes;
e) synchronization restrictions: width and thickness synchronization in case of several production lines, which are determined by restrictions in the rolling mill, and setup time restrictions on the continuous caster;
f) order restrictions: planning limit regarding roll performance, flatness restrictions, width adjustment; and
g) downtimes of the individual units that must be taken into account.
All installations that have restrictions regarding the transition between different process runs can be described and evaluated in this manner. Based on this evaluation, the production plan that is most advantageous from a process point of view is then generated.